HB9TMC

It is also possible to enable them via url parameter

wfts=waterfall timestamp: in seconds (2 to 3600)

I was told that hamstudy.org would be quite good for learning for the american exams, although I haven't tried it myself.

Regulations are often country specific, so that might not be helpful in this regard.

I think that will be the ARRL digital contest

https://www.arrl.org/arrl-digital-contest

If you have a separate computer running, you could use as well use the ft8 decoder from WSJT, for example using wsprdaemon or digiskimmer. It should give a fair bit more decodes.

Could it be that the kiwis IP adress changes after it was switched off?

That sounds like a power supply issue, I've never seen unexpected reboots.

Maybe you can see using journalctl whether it was a clean shutdown, in that case there would be something like this:

Dec 15 11:27:44 kiwi systemd[1]: Reached target Shutdown.
Dec 15 11:27:44 kiwi systemd[1]: Reached target Final Step.
Dec 15 11:27:44 kiwi systemd[1]: systemd-reboot.service: Succeeded.
Dec 15 11:27:44 kiwi systemd[1]: Finished Reboot.
Dec 15 11:27:44 kiwi systemd[1]: Reached target Reboot.
Dec 15 11:27:44 kiwi systemd[1]: Shutting down.

Another possibility would be that the kiwi's power supply has a Class-Y capacitor that leaks common-mode voltage to the DC side, which is then coupled trough the loop to ground.

In that case you could measure an AC voltage between the Kiwi GND and PE.

They do look like pileups, I think there are some dxpeditions. C21MM and PX0FF.

Did you add the subnet? /32 for single IP-addresses, like a.b.c.d/32.