Brand new install of Home Assistant OS on a Raspberry Pi 3. When I try to install add-ons, I get this message:
‘AddonManager.install’ blocked from execution, supervisor needs to be updated first
I would prefer to not update anything ever again. Last time I did, I lost all my mushroom cards. Is it really not possible to stay on a version that is known to work? Do I have to update, even if it breaks stuff?
Yeah that’s really not how you should consider using Home Assistant. Updates are released monthly. Sooner or later there will be an update you need for security, or a new feature you want to use. The further you fall behind the harder it will be to update. Try to stay up to date.
If you are concerned about things breaking automate nightly backups that are copied off your system. Restoring a backup takes 10 minutes at most.
Here is a list of backup applications that make this easy for you: https://www.home-assistant.io/common-tasks/os/#copying-your-backups-to-another-location
Yeah, I figured the answer would be something like this 
Fair enough - I will try to stay up-to-date! Thank you.
Well, technically, you can do that right now.
Just stay on the same version of everything you are on right now and you never have to update ever again and things will likely stay working barring any outside integration API changes.
But as was pointed out you won’t be able to add new things as they get released or get fixes for those outside changes.
That’s a huge trade-off but people do it. It really depends on your goals/needs.
Does the supervisor no longer auto-update?
I update my production system very rarely. I’m still on core-2022.4.5 at this time and I don’t plan on updating before next year. Having a reliable and working home is a lot more important to me than some random new feature. Things like this is the textbook example of why I don’t update. Don’t change a running system if that system does everything it’s supposed to do.
Security is a good point. But updates patching actual serious security issues are rare. If you keep everything inside your LAN isolated and use a good VPN for external access, then you should be on the safe side anyway. If someone can get into your LAN, then you have more serious problems than Home Assistant. If something really serious comes up, I just apply the patch diff without updating the rest.
Lastly, people will usually argue that it’s less work to keep up with changes if you update incrementally. While that may be true for people using a myriad of integrations, it’s not for me. I don’t want to be bothered with having to babysit HA all the time. HA is supposed to make my life easier, not be a constant maintenance chore. I keep HA very loosely coupled to my home automation backend for that reason with very few integrations (pretty much everything is MQTT based here). I don’t use the Supervisor either. One big yearly update is ideal for me. YMMV of course, but your profile suggests that you’re not that bad with tech 
Not after a certain update. I saw that the auto update was being removed but now there are also warnings logged that you can’t update or add new add-ons if its not up to date. But I can’t remember where I saw it tho.
I think that’s what the OP is seeing.
Edit: here it is:
Post 22 and 23.
You have to disable auto-updates for supervisor, manually.
I’ve been using home assistant about two years, and the only thing that seems to break regularly is z wave JS, which typically gets patched in under 24hrs typically due to compatibility with the new HA supervisor/core version. I’ve got a good subset of add-ons(~30) and lots of HACs integrations.
So to avoid that schedule my supervisor and core updates 48hrs after the last core/supervisor update. Ie just postpone upgrades until 48hrs after release, and you likely should never have an issue with upgrades.