Excluding 4x's and Jagged Alliance-Like titles
I'm meaning more 'chessboard' titles which feature a small set that you arrange your
characters on at the start of the game

I was playing Fell Seal and uninstalled it realizing there's much better out there to get through first.

Here's my picks:

Final Fantasy Tactics Advance
https://www.youtube.com/watch?v=_RI_mIFuSzc

Mordheim
https://www.youtube.com/watch?v=6lP740fLHFM

Dynasty Warriors Tactics 2
https://www.youtube.com/watch?v=eLT4GO-JHbQ

Ring of Red
https://www.youtube.com/watch?v=MwL_oDMXxYo&list=PLNfQgFiHOvvS-QB4GfA8V2o0mhqUNOniB&index=6

Warsong
https://www.youtube.com/watch?v=7L-NNBZVQkY

Shining Force
https://www.youtube.com/watch?v=ONKhXLJwpk8&list=PLKua6Rkz_ciyIomxRx6EhzHAx2hgbYzV0&index=9

Valkyria Chronicles
https://youtu.be/0FURscTVLkc

I'd like to personally throw in my two cents by mentioning Vandal Hearts 1 and 2, for the PS1. Both are great, but I personally enjoyed 2 more than 1, it's got a dual movement system that is quite easy to master and make pretty much any battle go your way once you figure it out.

Daisenryaku 7 and Perfect 4.0. Deepest TBT games there are, without compare.

The latter didn't receive a complete translation, but it's good enough that you don't notice after playing for a while and, if you follow some of the positive review's advice on Steam, you can mostly finish the job.

Into the Breach

Yggdra Union

Elven Legacy and Fantasy Wars were fun.

Oof, including consoles that's a big ask.

Final Fantasy Tactics (still the best)
Tactics Ogre: Let Us Cling Together
Disgaea series
Fire Emblem Series
Stella Glow
Makai Kingdom

X-com/XCOM series
Xenonauts
Phantom Doctrine
Stellar Tactics (promising game in early access atm)
Massive Chalice (so-so)

Then it gets muddy. Do Divinity Original Sin 2 and Shadowrun count? The Banner Saga? Wasteland? Invisible inc?

My understanding is that "Turn-based Tactics" = games that focus exclusively on the combat aspect.

Something like XCOM falls under "Turn-based Strategy". It involves maintaining your base and allocating resources.

Other stuff like Original Sin, ShadowRun & Wasteland fall under turn-based RPGs/Strategy RPGs.

Like a lot of games though, genre terms can be a bit muddy.

I haven't played many pure 'Turn-based Tactics' games. I really liked the Advance Wars games though.

how about The Battle for Wesnoth?

Incubation is on gog (in a bundle) and still a fantastic game.

Invisible, Inc.

What GreasyDogMeat said but yeah looking for those types of games as well
Personally I like base management and sending out away teams while I directly control another
X-Com, FF Tactics Advance, etc
My favourite is ROTK Online but refuse to play it because it's a Pay 2 Win - if only they could do ROTK for the PC in the same style but instead ROTK went the way of the early Nobonunga games. I'm watching a Youtube for it:
Very unique!