Without asking you to specify which almshouse charity your mother is accommodated by, all I can say is that it sounds most unusual for someone living in an almshouse to have a tenancy. The general model is to provide licences to occupy charity owned accommodation.
The recognised definition of an almshouse is:
An almshouse is a unit of residential accommodation (usually a house or flat) which belongs to a charity, is provided exclusively to meet the charity’s purposes (for example, the relief of financial need or infirmity) and is occupied or is available for occupation under a licence by a qualified beneficiary.
An almshouse charity is typically a charity which is established for purposes which are to be furthered by the provision of one or more almshouses.
An almshouse charity is usually a charity for the relief of financial hardship by the provision of housing and associated services or benefits which must (or is authorised to) provide its primary benefit by the grant of a licence to occupy the accommodation that it owns to its beneficiaries.
https://www.almshouses.org/what-is-an-almshouse/
Can you provide a link to any almshouse charity that provides proper tenancies?
Lots of almshouses do provide sheltered accommodation, i.e. independent living with a warden on site, hence the bit that alarmed you in the guardian article about pressing a green buzzer in the morning to check in. Almost all almshouse accommodation is aimed at older residents. According to your second Guardian article, 'residents typically move into almshouses in their early 70s'.
I can see that the almshouse movement is keen to expand its offer as an alternative to social housing for residents of all ages but currently it's almost all retirement (over 50's) or sheltered accommodation.
Yes, I am well aware that this is not the same as exempt 'supported accommodation' but the bottom looks about ready to fall out of that particular model. Meanwhile the entire rental market continues to spiral round the plug hole with LL selling up and rents skyrocketing.
It's a piece of piss for wealthy 'benefactors' to set up 'charities' to provide housing. Why wouldn't dodgy investors move their money into this field as other fields collapse? Why wouldn't the government also exempt this kind of propert if they provide 'services'?