(I tried to install flatpaks in 18.2, but never got anywhere due to errors such as "Invalid crypto engine" "Unable to complete signature verification". I don't know if that has anything to do with my current problem. I purged flatpak completely before I upgraded to 18.3.)
This is what my Flatpak page looks like:

(Except for the black bar. I't just in the image, not the real window. Dunno why that happened.)
When I start it from the terminal, this is the output:
Code: Select all
$ mintinstall
load_cache took 330.564 ms
add_categories took 9.805 ms
build_matched_packages took 0.123 ms
The Flatpak remote flathub could not be scanned: g-io-error-quark: GPG: Unable to complete signature verification: GPGME: Invalid crypto engine (0)
add_packages took 1509.072 ms
process_matching_packages took 1.604 ms
add_reviews took 907.619 ms
Downloading new reviews
update_reviews took 1285.887 ms
add_flatpaks took 2693.059 ms
__init__ took 3106.776 ms
Overwriting reviews file in (home dir)/.cache/mintinstall/reviews.list
update_reviews took 510.413 ms
(Otherwise, Mint is just becoming more and more awespme, so hefty cheers to Clem and all contributors!)