Just going to XO / Home / Pools / pool-1 and pressing "Add hosts" button, selecting host-2 worked OK this time. So no detaching host from a pool and attaching to new pool ... just a button

@BenjiReis Thanks. So what are my exact steps please?

I have 2 pools with 1 host each. Each host is master of its pool. (this is what you get by fresh installing xcp-ng on second machine and adding it in XO / New / Server)

I want one pool with 2 hosts.

Do I just go XO / Home / Pools / pool-1 and press "Add hosts" button selecting host-2?
Do I still need to execute xe pool-certificate-uninstall on host-2 ?

Last time I tried it I got some weird errors everywhere, but that might be because of botched Patches upgrade, I was impatient.
Thanks!

@McHenry Hi. Could you, please, list exact steps you had to do?

Im in the same situation as in your original post. If I open first pool and simply try "Add hosts" button, and add second host, the first pool shows second host, but XO / Settings / Servers only shows first host.
And xo-cli server.getAll shows second host as "status: 'disconnected'.

So after you did steps by @BenjiReis, what exactly did you do after?
When you say "move a host out of it's pool", ho do you do that?

I'm trying to solve this for more than a day now.
Thanks!