What is the sealing mechanism of UHV view ports & electrical interconnects?

Questii

Knife edges on the edges of flanges with a maleable material gasket like copper is often used for creating UHV chamber environments.

For UHV view ports, typically say quartz or some other material, how is the UHV seal accomplished?

Is it the same mechanism? E.g. knife edges machined on quartz windows and then encapsulated by two UHV chamber 'rings/flange cover' with a gasket inbetween the two mating surfaces?

What about electrical interconnects/feedthroughs? How do you seal them to create UHV (and still create electrical insulation because UHV chambers are often metal and you cant generally use polymers because of outgasing)? Do they use ceramics between the metal connects and the chamber or high purity polymers/epoxy like polyimide?

How is the UHV seal maintained for electrical feedthroughs also?