The kasa's can be hit over your local network through an API to turn them on and off. You'd need a bit of coding, but could run it from whatever device. If you have a raspberry pi, you could even install reef pi on it and do it that way.
All that being said, I think it's probably a terrible idea
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Any device remotely connecting to your kasa strip is going to have its reliability limited to that of the kasa, the connection, and the controlling device. The kasas are better than other devices for that, because of the local network connectivity (no external dependency), but you're still limited to your WiFi connectivity + assuming the controlling device acts in a realtime manner (in the realtime system sense). Linux itself isn't even technically realtime compatible.
The failure cases include the timer not triggering (minor) or the power on triggering and then the power off not triggering (catastrophic). I personally would feel comfortable with the kasa controlling something I can secondary monitor (eg temp) or something that fails safely (eg a light stuck on or off) or can run for a long time with only minor issues (say an ATO with a small reservoir). I think once you get into the state where you're dumping something into your tank and if it runs longer than expected everything dies, you should invest in something suited for the use case.
A pi running reef pi on a DC out feeder jack I'd probably trust, at least enough that if it killed everything I'd feel semi justified. If the kasa has an API to control a timer in seconds I'd probably trust that too. Beyond that I'd look for a normal solution.
