PavelDuda , Hello.
The only way to upload a certificate to a Teltonika device remotely is FOTA WEB. There is no remote command to upload a certificate. But I would highly recommend you using FOTA WEB. Because now you don't need to use it by yourself actually: you can delegate it. Create an agent and apply FOTA WEB connector. I am pretty sure there will be no problem asking it to upload TLS certificates, update configuration and ask it to apply certificates work for flespi channels too. If you have more questions about it, please use chat (top right corner of your flespi.io account) to ask for details.
