Is a conventional mortgage or loan with interest halal?
Short answer: No. Interest (riba) is forbidden; a loan that requires paying back more than was borrowed is riba, however it is named.
Allah says: “Allah has permitted trade and forbidden riba” (al-Baqarah 2:275), and the Prophet ﷺ cursed the one who consumes riba, the one who pays it, the one who writes it and its two witnesses (Muslim 1598). Any loan with a condition of paying back more than was borrowed is riba. Muslims should look for genuinely Sharia-compliant alternatives (such as true murabahah or musharakah after checking them with scholars), save to buy, or rent. This is not personal financial advice.
Answered according to the Quran and authentic Sunnah as explained by the scholars of Ahl al-Sunnah wal-Jama‘ah. For your own situation, ask a trusted scholar.