Can confirm, that this fixes my issue!

Cool!
This would certainly reduce the size of the card, however it would make it incompatible for people running versions of HA prior to 0.80.0 (where Lit was introduced).

Very true. Could include an additional ‘or’

I changed this in the top line of my file and didn't have any luck, still the same issue even after a restart of HomeAssistant

@ZinkNotTheMetal doesn't require a restart, you need to clear your browser cache, however

@iantrich thank you sir!

Very true. Could include an additional ‘or’

Yes, but the build process would then import LitElement anyway.

If it wasn't for the lost backwards compatibility I would merge this now.
But then again, people running Lovelace UI and Custom cards are probably keeping their HA fairly up to date, or what do you think?

Yea I guess these people have a update to date HA. 0.80 is also 5 version behind, so for me this step would be ok

@kalkih I think a note saying that future releases are only supported by 0.80+ is fair.

Thanks for your feedback.
I'll merge this at a later stage, I want to release version 1.0.0 first, so that people unwilling to update their HA at least get that version.

@kalkih
I did some tests on the dev branch of HA, we upgraded lit to 2.0.0-rc.2, and it does not appear to be playing nice :( Haven't done enough testing to know for sure that it can't be worked around, but not being able to ensure the version of lit your card is using means that it is more likely that core updating will break custom cards. Specifying the actual version needed, without ^, is probably the better update for now.
@thomasloven, do you have anything to add to this discussion? Whatever we decide here is going to be what I recommend to other lit custom cards as well. Thanks all.

Interesting, that could indeed be an issue and cause to cards break, especially with lit and lit-element still being young and developed quite extensively.

For now, my build process solves the issues related to externally loaded dependencies by bundling them in, the drawback being the additional size of the card.

I'm going to remove the ability to use the source directly in the next release, since people still seem to do it, and it's causing unnecessary confusion and issues.

I like the bundling idea and might see about adding to mine and suggesting it to others