Shortly having some electrical work done at my house, so the power will be on and off repeatedly for a couple of days.
Is there a (type of?) UPS device I could install to protect against the router going offline - say an hour or two of backup ? Second question - is Hub5 the same power connection, ie would any UPS I get for the 4 still work with the 5 when I get one ?
Assuming you will still have power to the supplier's cutout fuse in your home during the work, ask your electrician to wire up a temporary board for you while the electrical work is taking place (to run things like your fridge, router etc.). That should be a common request for most electricians now with so many people working from home.
A simple domestic UPS generally won't keep equipment running for that long. It is designed for short power cuts (minutes in length) until the power comes back on.
Portable 'power bank' type devices are also quite common now, and are designed to run for longer, but are pretty expensive for what they are. Your electrician may possibly have one for customers to use when the power is off.
Are you looking for a solution just for the period of the planned electrical work or are you thinking of power backup for use in the longer term?