This was reported to me on Matrix and I had reproduced the issue. Both on
snapshot 20240627.

Since updating, desktop capture no longer works across multiple compositors. I
had tested multiple compositors, sway and river.

Relevant logs

systemctl status --user xdg-desktop-portal
```
Jun 29 06:18:24 Tylwyth systemd[2539]: Starting Portal service...
Jun 29 06:18:24 Tylwyth systemd[2539]: Started Portal service.
```

systemctl status --user xdg-desktop-portal-wlr
```
Jun 29 06:18:24 Tylwyth systemd[2539]: Starting Portal service (wlroots
implementation)...
Jun 29 06:18:24 Tylwyth systemd[2539]: Started Portal service (wlroots
implementation).
```
systemctl status --user wireplumber
```
Jun 29 06:21:40 Tylwyth systemd[2539]: Started Multimedia Service Session
Manager.
Jun 29 06:21:40 Tylwyth wireplumber[36783]: default: Failed to get percentage
from UPower: org.freedesktop.DBus.Error.NameHasNoOwner
Jun 29 06:21:40 Tylwyth wireplumber[36783]: wp-event-dispatcher:
<WpAsyncEventHook:0x555a5bfd7f70> failed: <WpSiStandardLink:0x555a5c00bc00>
link failed: some node was destroyed before the link was created
Jun 29 06:21:40 Tylwyth wireplumber[36783]: wp-event-dispatcher:
<WpAsyncEventHook:0x555a5bfd7f70> failed: failed to configure si-standard-link
<WpSiStandardLink:0x555a5c1c6b60>
Jun 29 06:21:41 Tylwyth wireplumber[36783]: [0:35:20.234047080] [36783]  WARN
IPAManager ipa_manager.cpp:154 No IPA found in '/usr/lib64/libcamera'
Jun 29 06:21:41 Tylwyth wireplumber[36783]: [0:35:20.234095802] [36783]  INFO
Camera camera_manager.cpp:284 libcamera v0.2.0
```