Anyone have experience using M42-EOS adapters with focus confirmation?

Hello, all,
First post so I hope I'm doing it correctly.
I'm an old hand with Canon EOS, starting out with a 620 film SLR in 1988.
Lately, I've been using a number of vintage M42 lenses (Asahi/Pentax Takumar of various focal lengths and Helios M44 58mm f/2 variants) on both my EOS 40D and 5D MkIV DSLRs.
As a 58mm f/2 or 50mm f/1.4 can be a bit fussy to focus on the 40D (as they become functionally a wide aperture tele), I've become interested in trying a "later generation" AF confirmation chip-equipped M42-EOS adapter to be a bit more certain of nailing precise focus.
As usual, there is a wide range of "advice" as well as products purporting to do this.
Whether it's true or not, I've seen warnings that chipped adapters can actually damage the computers in FILM EOS cameras. Also that some/all will not work on the 5D4.
Therefore, my question: Has anyone had FIRST-HAND experience using such adapters, and will they work with the 5D4 and film cameras in addition to my 40D?
Many thanks!