It’s easy to setup as part of your installation, a service to keep the clock up to date, just like with any computer, it’s essentially configuration. The only difference with the RPI is, as there is no battery typically when it is off it is completely off and no onboard battery powered clock, which is resolved by the clock on it being set automatically at boot time.
I see from the other link you supplied that you are or have installed Home Assistant Supervised. Welcome! I am surprised there is any issue with your time setting on the RPI, as the exactly perfect correct way to set up HA Supervised is specified here - all those steps include ensuring the clock (and everything else) is perfectly configured. To do it perfectly right though, you must follow those instructions to the letter.
HA Supervised is the most flexible version of HA out there but due to it’s complexity it only has a small reported number of installations. You can click on the legend (using that link) to hide or show the different installation types:
From what I have heard (third hand), Nabu Casa supposedly tried to get rid of the Supervised method of running the Home Assistant environment, but there was a huge amount of blowback from developers so they backed down and continued to support it. As I am concerned about the HA Supervised usage and want to very actively support the growth of the number of installations, I am more than happy to help with any issues you may have. I do not have a huge amount of time to help and I am not at all an expert (a pretty new I would say ‘intermediate’ level) but I want to as strongly as possible encourage you and help you to use HA Supervised…
Lastly let me say that if you continue to have any issues at all, it is very much worth it to back up your HA configuration, then start from scratch following these instructions (same link as above), then just restore your backup - it should only take you about an hour and you will not lose anything in your configuration. The best way to back it up I have found is to use this add-on - so install that and do a full backup before you blow away your installation (or just use this for backups regardless). I have actually done that myself a few times and my whole system is runing like a top -
Add it under Add-Ons - I have mine backed up daily 