So I had a quick chat with one of the developers and according to him in LS5 this should work.

And as expected, there are no plans to adapt LS3 for this change. It is in a phase where no new features should be added and I expect it to be EOL still this year.

So there are good reasons to move on to LS5.

Hello.
I was about to send the ticket when I received your message. Thank you again for your cooperation!
So I see it is not necessary to create a ticket and the solution is LS5 upgrade. I'll do it next week and if I have some problems with Analytics 4 again, I'll write.
Thank you again for being so fast and cooperative!

So I see it is not necessary to create a ticket and the solution is LS5 upgrade.

Not so fast, hahahaha. I would setup a test environment first, if your only reason to upgrade is Google Analytics. The developer wasn't 100% sure and tried to confirm with another one, but I don't have a definite answer. So if you want to make sure that it works, setup a test environment first and try it. If you are a user of this forum you should have a Limesurvey.org account and probably have a free tier instance of the SaaS service which runs on LS5. So you might not even have to setup a test environment but could test there. Have a look into your account here on Limesurvey.org.

So first test if it works in LS5, don't blame me for upgrading and not working.

But I think LS5 is worth the upgrade anyway.

Ok In both cases I should upgrade, as you said, the developers don't intend to fix problems in LS3, so...I'll try it next week and if it doesn't work, then I'll create a bug ticket and I'll post it here.

Real "problems" like serious bugs or security fixes are still applied to LS3 afaik. But the support of GA4 falls more under "new feature", I guess.

But yes, I would recommend an upgrade to LS5 anyway, because I think LS3 will reach its EOL soon. Now, there have been changes in the theme system between LS3 and LS5. So if you use custom themes and javascript workarounds, you will need to test them and most probably adapt them to LS5.

Thank you for the tips. We use only default themes, so I hope there will be no problems in that aspect.
However, I  saw  that there are some active survey right now, so is better to wait with the update a little bit. In any case, if there is a problem with GA 4 and LS 5 integration I'll make a bug ticket and I'll post it also here.