Hi Benny!
Thanks for getting in touch with us. Let me help you with this topic.
Unfortunately, there is no simple way or built-in option to use checkboxes for tag selection in the community form. It is possible, but would require some custom coding. As a reference, our themer’s guide provides an overview of how you can customize our plugins templates > https://theeventscalendar.com/knowledgebase/themers-guide/
This is also the case for creating new tags via the community form. I can really see the use of having such functionality or option built in, so I suggest you post that as a new idea in our User Voice > https://tribe.uservoice.com/forums/195723-feature-ideas so others wanting the same can vote for it.
Please let me know if you need help elaborating this idea.
Best,
Victor