The Hungarian and Finnish location and direction suffixes thing sounds a lot like latin case. Do you know off-hand if it’s related?
However, localtive-case systems of Hungarian and Finnish are much more developed than anything we see in Indo-European (Latin has at most 3 cases with locative/directional semantics; Hungarian has 9; Finnish has 8), so it's a different system anyway.
Structurally, Finnish endings are also quite different from Latin as the ending is always the same (almost, except for vowel changes), while Latin has an array of endings for the same function and you need to learn about declension classes of nouns to understand how to select the right one. Finnish 'cases' are more like suffixes like '-ne' or '-que' in Latin. E.g., '-ssa' or '-ssä' is 'in (location)': 'Amerikassa' 'in America', 'Sveitsissä' 'in Switzerland'. In Japanese the ending for 'in' is '-de' and in Tamil, it is '-il'.
This seems to confuse inflectional suffixes with analytic particles. Certainly -ne and -que in Latin are not suffixes; they are clitics, exactly analogous to the English articles a(n) and the (not usually considered "prefixes"). They are not part of the word after which they appear. In contrast, the -i in humi "on the ground" is a part of the word, which mutated into that form to express a locative use.
(As a side note, that is not at all the norm in Latin - location is usually expressed with a preposition, as in sub monte "under [at the foot of] the mountain". Humus is one of only a handful of words that preserve the locative case.)
I believe the situation for Japanese de is similar, with de being either a clitic or a fully independent word. I have no knowledge of Tamil or Finnish.
In agglutinative languages with freer word order, it is easier to argue that a locative morpheme is a suffix because it always appears with nouns, but absent any phonological processes that bind them together, one can always write them with a space and call the second part "locative postposition". In some cases, it is even unclear if an agglutinative language is very morphologically complex or just uses a lot of function words.