This might help
Today I sent 2 items via age verification postage on going to the ebays purchase a label I found the only option was UPS at a cost of £10.35 or there abouts ( this was more than the buyer paid for the item + postage I had my option as tracked 48 with age verification @ £6.27 I found that this couldn’t be purchased via eBay and can only be purchased on the Royal Mail app ( & not at my post office) you will also need a printer as QR codes are not an option a bit of a mission but finally posted off 2 items - take to post office as you would with other eBay postage - don’t forget to label and pack as for bladed items
