Question in the title... A recent flatpak update to an application has introduced new bugs that turnou to be a bigger nuisance that the bugs that are fixed.
I don't see anything that looks like a flatpak rollback command, but is there a reasonably safe manual procedure?
(from the Flatpak docs)
Downgrading
It is possible to downgrade an installed application (or runtime) to an older build.
First you look for the commit you are interested in; this example is with GIMP:
$ flatpak remote-info --log flathub org.gimp.GIMP GNU Image Manipulation Program - Create images and edit photographs ID: org.gimp.GIMP Ref: app/org.gimp.GIMP/x86_64/stable Arch: x86_64 Branch: stable Version: 2.10.14 License: GPL-3.0+ AND LGPL-3.0+ Collection: org.flathub.Stable Download: 108.9 MB Installed: 308.1 MB Runtime: org.gnome.Platform/x86_64/3.32 Sdk: org.gnome.Sdk/x86_64/3.32 Commit: 8003d469b2224a1abe54b45793c9692e822cacee860d94861f5fc5e43111a689 Parent: 3fdfdf0963ba67629f287092229d9f5659bc9a2eeb1158c060b09d8a603acbcf Subject: Fix CPU detection on GEGL build. (3b047adf) Date: 2019-10-30 00:56:11 +0000 History: Commit: 3fdfdf0963ba67629f287092229d9f5659bc9a2eeb1158c060b09d8a603acbcf Subject: Fix typo! (a752f7df) Date: 2019-09-02 20:28:05 +0000 Commit: 798d8cd8a6a2ccf1bf21c0f5e9749dd4d97ecd511a3af1922d6fedf6c26e3a7c Subject: Release GIMP 2.10.12! (1366fa63) Date: 2019-06-13 02:25:52 +0000 Commit: 451758521226112dd7d4e2c4ce7fadaa93f69ce58c2f1afb70fb057db81f5e57 Subject: Update to GEGL 0.4.16. (1d8cb1dd) Date: 2019-05-09 05:02:52 +0000 Commit: 5c8a3dc204a12d4695c5bb7e98ea3b3862d78e52c1cf0f9b021c1dae836ecc95 Subject: Build GTK+2 with more patches. (d7578706) Date: 2019-04-25 16:46:42 +0000 Commit: fdbcfcbb8e5a4a6f484674208c6bbdf96c6e37fe2df21983a444069e5949276f Subject: Release GIMP 2.10.10! (781c0f7c) Date: 2019-04-07 21:40:06 +0000 Commit: 81dc4a6595d81ef6fe7b563dc046cf6dec2856a9628c1b8ff3178bf0547e6490 Subject: Update some dependencies. (8cef7f17) Date: 2019-04-04 18:14:23 +0000 Commit: d0d12223774157ce64690d7096624741bdadc9490ac730ee2aa752eabf2ce0b1 Subject: Downgrade ibus from shared-modules (d5d82037) Date: 2019-04-03 20:07:35 +0000 Commit: 1c130cbfaec924ee87a98f541b451f8e527599b2efda3add51cb0f57b3806ac5 Subject: Add "org.freedesktop.FileManager1" bus access. (bbf1f104) Date: 2019-01-08 19:51:49 +0000 Commit: 1fcb2c783cf61e22ca6ed03df9f95d59785d5cbd668b50f9765693956f1eedeb Subject: Update babl dependency. (e7b662db) Date: 2018-11-16 22:41:23 +0000 Commit: b6186ed16c732603f5c317bbc42717e500c0077251f9e8035a3266924b9cd55b Subject: Release GIMP 2.10.8. (34b1d53c) Date: 2018-11-09 13:49:13 +0000 Commit: 0edfacfb334969b2fd5dc8d02cb1f0a5a98a833b24fdc6bb25ba3fb042df08a9 Subject: Update babl and GEGL. (efaecfbb) Date: 2018-10-27 23:52:37 +0000 So, if you wanted to go back to v2.10.8, you'd deploy this commit:
$ flatpak update \ --commit=b6186ed16c732603f5c317bbc42717e500c0077251f9e8035a3266924b9cd55b \ org.gimp.GIMP UPDATE: as Syco commented, using flatpak mask org.gimp.GIMP would prevent GIMP from being updated the next time you ran flatpak update; this was introduced in flatpak v1.5, just a few weeks before I answered this post.
Note that you can list the current masks using flatpak mask.
Also consider using the --user option depending upon the install location.
flatpak search <NAME>. For example flatpak search gimp. And to "unmask" the app in the future, flatpak mask --remove org.gimp.Gimp flatpak update ..., without the sudo. Else you'd be updating the root's packages.