This is a very weird collection of mostly 80s-90s shows (with some even weirder outliers).
A lot of these I remember hearing about at the time, but not watching. Ones I can speak to:
Brimstone – Enjoyed this one a lot. Maybe before its time.; I think the dark approach and twisted religious aspects would work better these day.
Andromeda – I watched some early episodes of this (it went 5 years, really?), but it never quite clicked in how it was written. The premise, though, is solid gold.
Time Tunnel – Crikey, how did this one get on the list? That said, as a little kid, I loved this show. I even had (dating it / myself) a green turtleneck shirt that I would wear to Kindergarten that I called my "Tony shirt".
In retrospect, I appreciated the stuff back at the lab (Whit Bissel! Lee Meriwether!) more than the poorly structured Doug & Tony plots.
Maybe my personal attachment distorts things, but I'd rate Land of the Giants as a more obscure Irwin Allen SF venture.
The Questor Tapes – I've watched the pilot / movie for this numerous times. It's sad that personalities got in the way of an actual series being made.
Ark II – I remember this Saturday morning fare. It was part of a series of post-apocalypse "Wagon Trail" type shows (realized or only piloted) that were popular in that era, with the added bonus (?) of being show on Saturday mornings.
15 Sci-Fi TV Shows You Totally Forgot Existed
Even geeks couldn’t get into these shows!
If I were compiling this list, I would include the not one, but two, series about Invisibility in 1975-1976 — The Invisible Man and The Gemini Man.
I would also add The Fantastic Journey …
https://www.youtube.com/watch?v=fqKEENAGSBo
… and Otherworld …
https://www.youtube.com/watch?v=U8idvQeM0kA
… and, of course, The Starlost.
https://www.youtube.com/watch?v=UMAi6u4Ps5A
The Mantis reminded me of a whole string of campy Friday night shows from the 90s. The two that come to mind are Viper and The Sentinel
https://en.wikipedia.org/wiki/Viper_(TV_series)
https://en.wikipedia.org/wiki/The_Sentinel_(TV_series)
Most of those I've never even heard of.
Dark Skies – watched the first EP.
Survivors – watched the first EP and saw that it was the standard horrible redo of a great old show, much like the horrible redo of The Prisoner.
Andromeda – watched the first 3 seasons and then Sorbo's ego drove the thing into the ground.
Logan's Run? And if we get into kid's shows – Land of the Lost.
+Al Hunt Oooh, loved Logan's Run (the TV show). And Land of the Lost (the TV show) rocked,