Learn Swedish: Visst är glampingen avskild, men prislappen är hög. - Admittedly the glamping is secluded, but the price tag is high.

In this concessive structure, visst (admittedly/sure) acts as an adverb at the start of the clause. Because Swedish strictly follows the V2 rule (the verb must be the second element in a main clause), the verb är has to come immediately after visst, pushing the subject glampingen to the third position.

Can I use another word for 'surely' like säkerligen instead of visst here?

Not if you want to keep the same meaning. The specific pair visst [X], men [Y] is a fixed argumentative structure. It translates exactly to 'Admittedly [X], but [Y]' or 'Sure, [X] is true, but [Y]'. Using other adverbs won't carry this specific 'conceding a point' function.

Glampingen is an English loanword. Do all English words ending in '-ing' become en-words in Swedish?

Generally, yes! English loanwords that end in '-ing' (like glamping, camping, dejtning) are almost always adopted as en-words in Swedish. Therefore, to say 'the glamping', you just add the standard definite suffix -en to get glampingen.

How is the word avskild (secluded) built?