You're more than welcome for the private message. It's all about spreading around the good fortune. So obviously when you know the answer help others who come to you.
Yeah, I'm not your software guy. Operating system I'm fairly OK with but in terms of the third-party applications of what people use and what works and what doesn't I'm not your guy.
What I probably advise you to do is to read the forms pretty well first because we have a mega commercial software thread going we also have a few other things and basically know that there's your primary 3D modelers, CAD, and Video effects systems are then there's a series of Adobe systems applications that you'll probably want. There's one famous Windows emulator for Windows 95 potentially upgradable to Windows 98, I don't remember, that you'll probably want.
You'll also want to know information regarding customizing your desktop like the settings backgrounds (terminal operation... no GUI for that!) and adding elements to your menu system and things of that nature. FAQs and searching for those terms should reveal the answers to those.
Please be aware that the forums here exist in kind of "on the fence" area where we don't really outwardly talk about where to get the software it's more what used to run and what is kind of "gettable" now. So obviously someone will be around to slap your hand if you're too far over the fence.
A few members run some software archive sites and they can PM if they feel comfortable showing their archives. Development libraries are much more open because again they're more platform only and not third-party. So if you're someone is interested in getting compilers and all that going, which is its own challenges and has its own groups, there's a neighborhood for that as well. Please note that there is no automated HTTP driven get package style manager for SGI.
There is a group that has gotten the RPM package manager to work on Irix and so the other SGI group on
http://sgi.sh does a lot of that kind of stuff and you'd want to go over there to figure out how that all goes, if you're interested. I stay away from all that myself.
There is a very old freeware OSS archive from an old site called NekoChan that we sometimes talk about because a lot of of us used to visit it before it collapsed, that had an integral native SGI tardist series of open source applications from circa 2003 to maybe about 2008 or so? Somebody can correct me on the finalization date. Those used to be the best go to open source packages back in the day. There is a movement of people trying to update that whole load of work but I don't know what the current status of any of that is.
Most installable packages are not going let you choose where to install them. The process is entirely automated. It's not like running make and specifying some sort of installation prefix. So once you're comfortable with your operating system you have two basic choices. You can either attempt to clone it to a much larger disk now that you're comfortable with not needing to erase the disk and reload it when you mess up or you can use an option disc and mount it into the various regions that the files exist in that you would care about like your home directory. I'm not sure how much space the mass installation of every goodie known to man would take up on an SGI.
While you should create a list of what you're interested in and start looking around for that, archive.org has a surprising amount of SGI stuff starting from about 10 years ago by the way. You should concentrate on making sure you understand the octane manual and all the warnings associated with it. That you familiarize yourself with YouTube videos showing Irix's installation as well as the instructions I've included from Ian's SGI depot about that.
And you need to find all the mods and hacks to customize the desktop including the mod to make a scroll mouse wheel work and things of that nature.
Also there is a command called chkconfig that turns off a lot of major services. There's a lot of excess services that are going slow down your machine, ESP is one of them, that you'll want to disable to get back runtime. Look up that as well:
https://software.majix.org/irix/admin-chkconfig.shtml
In terms of transferring files to and from your new system, FTP is normally started on SGI's when you install them. Enabling the FTP and simply using it to get files in and out of your SGI to your normal modern computer is going to be your easiest and fastest way to go. There have been people who have been working on newer SSH installs so that they actually agree with the newest cipher but I'm not up on all that and so I can't participate in that conversation. Internally I would just use FTP and get over with it. For the most part NFS can be stable under most situations but you have to install it in a very carefully using your overlays disks as well to make sure you don't install it wrong because else you get a lot of crashes and you won't know why. But NFS did generally work the last time I used it with like macOS but that was 10 years ago. So take that with a grain of salt.
I'll also say that just like modern computers when you keep an SGI plugged into the wall it's going to produce a 5 V standby voltage all the time which is still something you'll need to watch out for is the power supply ages. So I would personally recommend after you get your RTC figured out that you have some sort of switched power strip or you just don't leave it plugged in when you're not using it.
Just my two cents I'm finishing off where you might want to go.