Interesting :) to an outsider it can look a bit like Georgian or Armenian,
https://stasher.news/uploads/457
but it isn’t ;)

Given the pattern it’s almost certainly a substitution cipher (or a private invented alphabet) writing English.
Throw it at a decent LLM and it will probably crack most of it quickly (I can’t use good LLMs anonymously, so I can’t do that step for here you).

The poem is Longfellow's "A Psalm of Life" (1838), the first two stanzas, copied out in the private hand:

Tell me not, in mournful numbers,
Life is but an empty dream!
For the soul is dead that slumbers,
And things are not what they seem.
Life is real! Life is earnest!
And the grave is not its goal;
Dust thou art, to dust returnest,
Was not spoken of the soul.

It checks out against the page in ways a guess couldn't:

• Lines 2 and 5 both open with "Life is", which is the repeated pair I flagged earlier.
• Line 7 has the same word twice ("dust"), and its comma sits where the original's does.
• The crossed-out word in line 8 is where "spoken" goes, so the copier slipped and redid it.
• Word counts match the original line by line.

The key. It's a stripped-down Latin hand:

• Letters missing a stroke: Λ = a (A without its crossbar), 3 = b (B without its stem)
• Other shapes: 6 = d, 2 = e, Π = f, < = g, ∩ = h, | = i, ~ = m, 7 = t, the r is a loop, and V covers both v and w
• Raised vowels: o is a 0 or a small raised circle, u is often a small raised cup. These are the "diacritics" that threw everyone off.
• Unresolved: n and s are two similar loopy shapes I can't reliably tell apart at this resolution.

The letter is only partly readable, third paragraph (brackets mark uncertain readings):

Just wanted to say I love you guys. Thanks for everything that you do. Thanks also to [+name+] for creating [+name+]. It [is/was] a [nice?] idea and [I?] love the [...]

The first two sentences are solid. The "+" signs bracket names, which confirms what I suspected; I just can't read the names themselves.

Paragraphs 1 and 2, the closing line and the two names in the heart stay unreadable for me at this res. I can pick out scattered words like "we", "so", "but", "by" and "this is a ... way to", but not enough for a trustworthy sentence. The main trouble is the n/s pair and a few other look-alike shapes. Anyone with the physical sheet could potentially finish it using the key above.

Compared it against about 30 real scripts, including Thaana, Tai Viet, Sundanese, Batak, Ol Chiki, Kayah Li, Pahawh Hmong, Pollard Miao and Malayalam. Nothing matched. My best read is a constructed script or personal cipher. The marks above and below letters suggest vowels are written as diacritics, the way many Indian and Southeast Asian scripts work. The layout (two four-line stanzas with commas) looks like a poem. The crossed-out word in the last line suggests someone writing fluently in a system they knew, not doodling.

One lead I haven't ruled out is a fantasy script with vowel marks, like Tolkien's Tengwar, used to write English or another language. The letter shapes don't look like a good match to me, but it's worth checking.

Better places to ask:

• r/codes for cipher solvers
• r/conlangs, where people who invent scripts may recognize the design
• r/translator, which has an "Unknown" flair for this kind of thing
• Omniglot, which has a large catalog of real and invented scripts

On r/codes, mention that lines 2 and 5 begin with the same two words. Repeated words like that are what cipher solvers use to crack substitution systems.