That was the first thought that came to my mind when I saw the OP headline, though I read nothing else.

Any older hand or altar missal had Masses offered una cuм.....et Rege Nostro (in a 1806 hand missal which after the Mass has prayers for King George and Queen Charlotte). Our Saviour recognised Caesar under whose authority He was crucified. Catholic priests offering a Sarum Mass for a recusant family could mention Queen Elizabeth one Sunday and before next Sunday be hung, drawn and quartered under her authority. Even if sedes jeering refer to the SSPX rightly stating it is a prayer for the Pope, not an endorsement, it remains that. Benedict cleared out the pagan elements JP2 had put in his Assisi interfaith meeting, which while far from perfect, reached a minimum. Moreover, Summorum Pontificuм was a clear recognition that Montini could not, and never did abrogate the Mass. While it still put the problematic Novus Ordo rite on the same level, it gave the Mass standing. +Williamson and +Lefebvre were clear on the problems of the Novus Ordo but never held it was inherently not valid. Non una cuм was a theory advanced by +Guerard des Lauriers OP but the St Gertrude the Great priests unfortunately made it their own to frighten Catholics from hearing Mass at an SSPX chapel. It can be a theory for learned, licenced priests to ponder over, but nothing more.

Summorum Pontificuм is a docuмent of a man who was long ago horrified by the student rebellion of the sixties and mortified by the wilful blindness of JP2 to the depravity of Marcial Maciel and others (Benedict introduced a stable process to defrock priests which Francis crippled, giving particular attention to aiding wicked, wicked pederasts like Don Inzoli). It is far from perfect, but sadly there are so many who prefer nothing if the alternative be not perfect. Priestly and episcopal orders need to be fully restored, but SP is a start and not something to be rejected. Sede orders are themselves not without problems. The fact that Traditionis Custodis was ignored, even lightly jeered at by apparent Bergoglian allies like Cardinal Marx shows how Conciliarism is draining of authority.

Pope Benedict lives for a great purpose. Hopefully he can somehow speak more directly rather indirectly through comments relayed by others and a strange resignation which sees him still garbed as Pope.

+Williamson offered Masses in a hired room in a hotel near me until COVID and otherwise has used farmhouses (also SSPX chapels did the same at ever shifting times), stables and the open air. These are the catacombs of our times, and safer than graveyards as Irish Gardaí showed no shame in harassing Catholics offering prayers in one in defiance of the anti-Catholic lockdown rules.

Forgive the excess of words, and I hope I made my points clearly. God bless you all.

I mean, having my own parish be nothing more than a somewhat modified old rural schoolbuilding seems like the "catacombs" to me.

I mean, having my own parish be nothing more than a somewhat modified old rural schoolbuilding seems like the "catacombs" to me.