Old Flatpak version in Focal repo: no Chromium for me?

Tried to install flatpak Chromium, to no avail:

 5. [✗] org.chromium.Chromium                     stable           i            flathub           < 102.8 MB

Error: org.chromium.Chromium needs a later flatpak version
error: Failed to install org.chromium.Chromium: app/org.chromium.Chromium/x86_64/stable needs a later flatpak version (1.8.2)

Flatpak 1.8.2 is available starting with Groovy:

$ rmadison flatpak
 flatpak | 0.11.3-3               | bionic/universe          | source, amd64, arm64, armhf, i386, ppc64el, s390x
 flatpak | 1.0.8-0ubuntu0.18.04.1 | bionic-security/universe | source, amd64, arm64, armhf, i386, ppc64el, s390x
 flatpak | 1.0.9-0ubuntu0.1       | bionic-updates/universe  | source, amd64, arm64, armhf, i386, ppc64el, s390x
 flatpak | 1.6.3-1                | focal/universe           | source, amd64, arm64, armhf, ppc64el, riscv64, s390x
 flatpak | 1.6.5-0ubuntu0.1       | focal-updates/universe   | source, amd64, arm64, armhf, ppc64el, riscv64, s390x
 flatpak | 1.8.2-1                | groovy/universe          | source, amd64, arm64, armhf, ppc64el, riscv64, s390x
 flatpak | 1.8.4-1                | hirsute/universe         | source, amd64, arm64, armhf, ppc64el, riscv64, s390x

I guess I could remove the official Flatpak and use some PPA instead, but it would pretty much undermine the whole idea of getting your software from a trusted source. Snap Chromium is painfully slow on my system for some reason. (As well as snap Firefox.) So, any options left?

There is nothing to fear.

Official FlatPak setup guide https://flatpak.org/setup/Ubuntu/ lists the PPA.

So you have to open terminal and type:

sudo add-apt-repository ppa:alexlarsson/flatpak
sudo apt update
sudo apt install flatpak

flatpak remote-add --if-not-exists flathub https://flathub.org/repo/flathub.flatpakrepo
flatpak install flathub org.chromium.Chromium

Note: I'm using Ubuntu MATE 18.04 LTS, so the PPA is also needed for me.