Gigabit ethernet switch Desktop or Rack mount working or non (Erith DA17)

Hi
My internet provider has changed My internet setup and provided me with a new router but the new router they have given me only has 1 ethernet port and cannot connect any other important devices because I do not have any spare ethernet ports. I cannot change My router and I am being told I need a 10/100/1000 Mbit/s (Gigabit) ethernet switch.

I have tried using an old router as a switch trick but it is causing problems and My internet provider is telling me that this is not supported

I have seen people upgrading so thought I would post here and hopefully, someone has a Gigabit ethernet switch (Desktop or rack mount) in working or non-working condition
(I may be able to repair it).
I always like challenges.

Please if anyone has anyone, Let me know because I need to connect some important devices
Thanks so much in advance