That definitely appeared to be an active matrix screen. If it's a 540c, it almost certainly is. Someone COULD have swapped a 520c panel in, but that's extremely unlikely.
The screen in that unit should either be a Sharp LQ94D041, a Toshiba LTM09C017, or a Hosiden LCD without a model number...
Membrane keyboards are extremely difficult to repair, if possible at all. I'd recommend just waiting for a keyboard to show up, I'm sure you'll be able to find one eventually.
Ugh, yes, it is. It really sucks, because you can't get the right film to repair those. TFT Color displays can be fixed but passive matrix can't. You can sort of fix them, and they will work with the film you CAN get, but they won't look quite right.
The only storage practices I know of are to...
My first guess would actually be a video issue on the logic board. It could absolutely be the screen though, so try a recap if it’s a Sharp display. If it’s a Toshiba, or if the recap doesn’t help, it’s gonna either be the screen itself or the logic board.
You also have two issues there - the...
I do not necessarily think the PSU is at fault for this particular issue, but it MUST be recapped. The IIsi PSU uses ELNA LongLife Series caps which are the single worst in terms of leakage out of any I’ve ever seen. They’re replace on sight and you’ll regret not doing so later if you leave them...
Any of the following:
PowerBook Duo (all models) - not recommended because they have a Rifa cap in them
PowerBook 1400
PowerBook 2400
PowerBook 3400
PowerBook G3 (all)
iBook G3 Clamshell
The G3 Snow models use the later connector that’s smaller.
Those legs just look like they're bent backwards, I think that's fine.
Only booting one in 20 times is textbook bad capacitors. Get 'em changed and it should be stable again, hopefully. They don't have to look bad to be bad.
A PSU taking a while to start up sounds like a textbook case of weak capacitors to me, but with power supplies it could always be something else. Unless you're really good at troubleshooting switch mode power supplies, I'd recommend just recapping it.
Console5 has cap kits...
Apple didn’t get it in their laptops till 1999, they were late in that regard. Apple was never early to adopt USB, they were just early to remove legacy ports (iMac). Most PC laptops from late 1997 like this WinBook is from had USB. 2 ports was rather uncommon though.