If You connect to Your "LE Download folder" from Windows Explorer that should work without any hassle if You have the SMB sharing enabled.
( Sharing additional folders from LibreELEC via SMB [LibreELEC.wiki] )
Copy Your .zip's to "\\<IP adress>\Downloads" and paste .zip-files there (don't extract them!).
(no need to 'mount it, just connect using the address field)
You should now be able to find these files from Your LE file manager.
I'm pretty sure You're out of luck there at the moment...
AFAIK there is no Chrome/Chromium for any RPi.
[edit]
Unless LibreELEC-RR 9.x [ Emulationstation | Retroarch | Pegasus | DolphinQT | Moonlight | Chrome | Spotify ] has a working solution.
I haven't tried that on RPi
Does adding "Wait for network" to approx 30 sec make any difference?
If both/all clients are connected to same MariaDB instance there shouldn't be any need to do scraping from more than one client.
Movie/video/... info is stored in the shared DB including progress and watched status.
Thumbs on the other hand are stored/cached locally on each client.
You seen this: MySQL - Official Kodi Wiki and this https://kodi.wiki/view/mysql/setting_up_mysql
Does RPi4 have a web browser?
If it does, I wasn't aware of that...
Most people dealing with wireguard should be advanced users which have no problem using SSH.
Why? So normal/average users should not use Wireguard?
Correct naming should solve Your issue.
I added new series few days back using naming as stated in post #7.
No offense but;
As librelec.tv forum is English You have greater chance of getting answers if You ask Your questions in,well, English...
LibreElec (i.e. Kodi) versions MUST match so they use same DB version.
DB version (107, 110, ...) are tied to Kodi versions.
I'm not that sure that MakeMKV really does write .ISO files... 
Same result on both HDMI ports?
Start debug logging, run a library update and post logs.
Maybe more information at:
This isn't the most graceful way but still it does the job;
In the bedroom i run a small bash script with cron every night at 03:00
systemctl stop kodi
shutdown nowAt 03:30 the "smart power plug" cuts power to the RPi.
Day after, the power plug scheduler starts/power on the RPi at 16:00.
(If necessary, it kan be started with remote as well...)
... I'm not sure which setting made it work. ...
You can find all descriptions/explanations here: Video options in config.txt
For addons in general. You should start at 'forum.kodi.tv'.
Someone started a mega.nz addon for a while ago but it seems like it has died out...
Does it make any difference if You add 'Wait for network" delay (in LE settings) to say around 30 sec.
That should allow the network connection to be established before anything else loads.
--> https://libreelec.wiki/libreelec_settings?s[]=network#tab__network
The episode name/title isn't required.
I only name episodes like: "Seinfeld (S03E10).mkv"
Kodi picks rest of the info from (in my case) TMDB.
