EDIT : It works !!

so we have 2 devices, such as 2 smartphones, not same age not same brand but both android.

on device 1 we have bookmarks.

on device 2 we have zilch. nada.

step 1 Take device 1 & create an opera account using YOUR email as identifier and anything you want as a pwd. Note them.

step 2 log in your email and validate your inscription (a link is provided).

step 3 bottom right red opera logo, click on settings (lower left option in tiny window) and then on top of menu opt for "synchro & baxckup" near what looks like an avatar

step 4 get a cup if tea. Then with device 2, connect to the existing opera account with credentials as per above 1) & finish your cup of tea.

step 5 now put device 1 in front of you and start opera. You should have all the quick access webpages listed.
open the first one and note what is written after www: of the first saved link : then take device 2, start your browser- you have no bookmarks- & enter what is written on device 1 : as an exemple if your first bookmark on dev 1 is *www.lovestoryneverlastlong. com" when you enter "love in device 2, it will auto-complete with "storyneverlastlong. com" : at this step you only need to save the entry on device 2 using the 3 vertical dots on top right of page and then "add to" option.

Et voilà !!!