This seems to work with extensions.gnome.org for me, but 1Password and open_with don’t seem to be able to talk to their native apps.
I managed to capture logs from Firefox startup, if that helps
[Parent 12521: Main Thread]: D/NativeMessagingPortal creating session with handle suffix firefox_open_with_540547117
[Parent 12521: Main Thread]: D/NativeMessagingPortal session created with handle /org/freedesktop/portal/desktop/session/1_242/firefox_open_with_540547117
[Parent 12521: Main Thread]: D/NativeMessagingPortal starting open_with, requested by openwith@darktrojan.net in session /org/freedesktop/portal/desktop/session/1_242/firefox_open_with_540547117
[Parent 12521: Main Thread]: D/NativeMessagingPortal native application start requested in session /org/freedesktop/portal/desktop/session/1_242/firefox_open_with_540547117, pending response for /org/freedesktop/portal/desktop/request/1_242/firefox/260106597
[Parent 12521: Main Thread]: D/NativeMessagingPortal got response signal for /org/freedesktop/portal/desktop/request/1_242/firefox/260106597 in session /org/freedesktop/portal/desktop/session/1_242/firefox_open_with_540547117
[Parent 12521: Main Thread]: D/NativeMessagingPortal native application start successful in session /org/freedesktop/portal/desktop/session/1_242/firefox_open_with_540547117, requesting file descriptors
[Parent 12521: Main Thread]: D/NativeMessagingPortal got file descriptors for native application in session /org/freedesktop/portal/desktop/session/1_242/firefox_open_with_540547117: (192, 207, 208)
[Parent 12521: Main Thread]: D/NativeMessagingPortal session /org/freedesktop/portal/desktop/session/1_242/firefox_open_with_540547117 was closed by the portal
[Parent 12521: Main Thread]: D/NativeMessagingPortal cannot close session /org/freedesktop/portal/desktop/session/1_242/firefox_open_with_540547117, unknown handle
[Parent 12521: Main Thread]: D/NativeMessagingPortal will be used
[Parent 12521: Main Thread]: D/NativeMessagingPortal is available
[Parent 12521: Main Thread]: D/NativeMessagingPortal creating session with handle suffix firefox_com_1password_1password_60275599
[Parent 12521: Main Thread]: D/NativeMessagingPortal session created with handle /org/freedesktop/portal/desktop/session/1_242/firefox_com_1password_1password_60275599
[Parent 12521: Main Thread]: D/NativeMessagingPortal starting com.1password.1password, requested by {d634138d-c276-4fc8-924b-40a0ea21d284} in session /org/freedesktop/portal/desktop/session/1_242/firefox_com_1password_1password_60275599
[Parent 12521: Main Thread]: D/NativeMessagingPortal native application start requested in session /org/freedesktop/portal/desktop/session/1_242/firefox_com_1password_1password_60275599, pending response for /org/freedesktop/portal/desktop/request/1_242/firefox/1460337894
[Parent 12521: Main Thread]: D/NativeMessagingPortal got response signal for /org/freedesktop/portal/desktop/request/1_242/firefox/1460337894 in session /org/freedesktop/portal/desktop/session/1_242/firefox_com_1password_1password_60275599
[Parent 12521: Main Thread]: D/NativeMessagingPortal native application start canceled by user in session /org/freedesktop/portal/desktop/session/1_242/firefox_com_1password_1password_60275599
[Parent 12521: Main Thread]: D/NativeMessagingPortal session /org/freedesktop/portal/desktop/session/1_242/firefox_com_1password_1password_60275599 was closed by the portal
[Parent 12521: Main Thread]: D/NativeMessagingPortal cannot close session /org/freedesktop/portal/desktop/session/1_242/firefox_com_1password_1password_60275599, unknown handle
[Parent 12521: Main Thread]: D/NativeMessagingPortal will be used
[Parent 12521: Main Thread]: D/NativeMessagingPortal is available