Please don't make it a paywall. (Heck, I made my first purchase 2.5 years after joining...)
And remember the time when they DID block certain number sequences and that caused all sorts of problems with posting links (containing numbers) or prices or various other things?

But isn't something checking for actual human input required to make an account? If a bot gets past that, it'd get past a repeat of the check on the forum too. So maybe it'd help, if done in a very limited way, say for an user's first 10 posts, as otherwise it'd get too annoying for new users, but probably not as much as it may seem.

A limit on the number of new threads and maybe even posts per time unit for the first X posts may also help, but again may also harm legitimate new users.

But most important is to have active moderation 24/7, as any major community should. Heck, even if someone just glances at the recent topics list once or twice an hour, everything would be cleaned up before most would be affected by it and those users would be swiftly banned.

PS: As for the suggestions to change the forum as a whole, again, considering how badly GOG messed up with any change or redesign, please don't. Flawed as they are, they're absolutely certain to be far less bad now than anything new that they'll implement could ever possibly be.

Spam patterns are quite precise. Writing regular expressions in accordance with them will not cause any problems to normal users.
Those examples do not resemble titles of any spam threads.

I have replied directly to post proposing to ban certain words.

They don't even need new code, just a competent implementation of anti-spam controls. SomethingAwful runs on vBulletin Version 2.2.9, which one might note is a few versions old.

It doesn't even have to be a true paywall, just redeeming a refunded fee or a free game would be enough of a litmus test that the person or being is approximately humanoid enough to be on the forums.

...aaaand g.o.n.e :)

Probably the forums GoG is based off of using is old and they don't think it's worth putting any effort into, or if they change something they will break it. And no doubt the entire forum is based off a template and modified to make a unique look, so just upgrading or changing something doesn't quite work.

Though i would...

Forget it
Try to find your own opinion based on the posts exchanged here:

gog.com/forum/general/celebrate_gogs_14_years_of_making_games_last_forever_432a7/post116

So, your answer to a rat, mouse or other infestation, is to blow the house up ?, just to be sure...

What the forums needs is mods from different timezones, so there's forum coverage against attacks, on deck, basically all day every day.
On the weekend just gone, the spam bots could run rampant, because the mods were bunched in one timezone, and the mods were not on deck on the weekend.
We need mods to be from different multiple timezone regions. Mods from Europe, North America, Asia/Pacific. Have mods from timezones in those regions, and you get more thorough coverage and protection for the forums.

I'm all for this. It allows "free" accounts to still contribute something or ask for help on the forum, and the last one would help to weed out at least the current bot posts, especially the phone number filter because it'd target the current bot patterns without impacting on anything legit.

But all this needs to be supplemented with at least one mod which can work on weekends to clean up the remaining bot posts.

I think one problem with recruting potental moderators is that anyone who potentally would be a mod tends to have extreme ideas towards moderations.

For example, I'd bamf this thread as an unwarranted necro.

I'd also soft lock most threads older than 90 days and make it a bureaucratic process to get them unlocked. NFTs would be a banned topic, and I'd make a clear statement towards the current operating system support stance, warning that only wolves and dragons await those on old systems.

There are also several people who I would have banned from the forums, but they've stopped posting. I'd preempt some announcement threads by not allowing discussions on them in the first place, pending any word from Moses.

I'm a pretty new user on the forums. For me definitely biggest hurdle when entering is the unintuitive structure and layout. Odd notifications, hard to follow attended threads and all seems just to be dumped into general discussion without any categorization.

I'd have also banned the poster who did that necro, for point blank refusing to use brains and intelligence, before posting.
Pointless necro, and brain dead over quoting.

Stop lying to yourself, and everyone else on here, about being a newbie on the forums.
Your account was registered back in December 2013. That's MORE THAN 2 YEARS before I created my account on GOG. The Community General Discussion area is where all the threads that are NOT about specific games/series, go.
To see all the games GOG has forums for, page top bar -> COMMUNITY -> All forums
On the all forums page, scroll down till you see "show all 3380 forums" click that, and wait for the full list of forums about specific games/series, to load.

You can have an old account AND never use the forum until now. The account date has nothing to do with forum use afaik.