Not sure what your experience is. For the sake of this I'll assume you're brand new
I only started playing pugs recently after adding up for a couple months and having a 90%+ unpicked stat. it takes a while.
TF2center and TF2PL are options, though they're not the best. It'll teach you the very basics like where to hold and how to not overextend into multiple people but in general the games are not very organised. Good place to start if you're new to this, though you'll want to move on after a couple months. TF2PL will be more balanced but I'm uncertain how alive it is, TF2center has a large range in skill levels so you might end up against or with the entire spectrum of skill levels.
There's an EU mixes discord. I've not tried it myself but they organize multiple games each day and from what I hear there's occasionally open/brand new players in them. From what I've seen so far most players were somewhere between low-mid that play regularly. At least the few names I recognized. I'll PM you an invite link.
I cannot tell you what you should expect because I'm not familiar with the regulars there. Though they'll probably be welcoming. If you're not comfortable playing immediately you could ask them if you can spectate and listen to a team's comms to get an idea of what it's like (people with admin rights should be able to move you into other channels even if the voice channel has reached its player limit)
edit: just to clarify I was talking about the "EU Mixes" discord. if there's other beginner friendly mix discords, send invites Dayne's way :)