I am currently using Ubuntu 20.04 with an integrated GPU. Recently I was unable to play the No Mans Sky game because the GPU was not being used.

In an attempt to cure this (before I knew how to upgrade the kernel), I installed 21.04. This ran ok but booting the game gave a black screen so I reverted to 20.04 which involved a complete reinstall.

Later I upgraded the kernel to 5.11 and following a number of usual software updates the game can now be played although I only get 20 FPS.

When grub boots I get a number of errors which 'go away' and the boot continues.

I am asking for advice on whether to stick with what I have until the new LTS version or to make the full upgrade to 21.04?

Will I gain anything and would there be any risk using a non-LTS version?

I do have my /home on a separate partition so I lose nothing but have to reinstall programs.

BTW, Ubuntu 21.10 is already out. And the next LTS 22.04 comes in April 2022, so it's not such a long wait.

You should check these errors and repair if something is wrong. Check "journalctl -b", CTRL+1..12, or just record video to see them.

If you use some components from another version of Ubuntu or other distribution, then there can be some incompatibilities. I don't think newer kernel would be problem, rather some libraries or software dependend on each other. Better is using "full" versions LTS or temporary, which was tested by community some time. If you mean that you ugraded to non LTS version (temporary), then it has only new versions of applications, less tested, but should work. There is always risk, that something will not work, even in LTS.

Did you tested this game on Proton, it has Gold rating.

As has been mentioned the latest version 21.10 is out now if using non-LTS version then this is the one you want. It will have even newer kernel perhaps offering better support for your machine's graphics performance. The errors you see during start are not errors at all if so the boot would fail. Most likely it is like I see every time I boot, with the waiting for ZFS import I see with the timer going until the cache loads and the boot proceeds when it does. You get a 5.13 kernel plus the upgrades to all the other software in the system to close to current versions, there is always a little lag behind depending on when the cut off line is set for inclusion. Only way to find out if it improves it for you is to install and try it.

journalctl -b 'errors':

Yes, I installed 21.10 before it came out then reverted to 20.04.

Having read the posts in the answer, I think I should wait for the next LTS version. The system works so I think there is no point today in taking a risk.

Thanks all for the input.

That is not really worth worrying about just another manufacturer with garbage for their implementation of the DSDT contained on the board. Since the boot succeeds nothing really needs to be done unless you experience problems. One of mine has "TSC_Deadline fails errata not implementing" or something like it I get then it continues on its merry way.

I am using kernel 5.13.0 and as you say, "it continues on it's merry way", so leave well alone for the time being.