gg5, prog, luminous

Definitely should be split. I think ふるあと can be dropped.

@@ -10,3 +9,0 @@
-<keb>古跡</keb>
-</k_ele>
-<k_ele>
@@ -15,9 +11,0 @@
-<k_ele>
-<keb>古蹟</keb>
-</k_ele>
-<r_ele>
-<reb>ふるあと</reb>
-<re_restr>旧跡</re_restr>
-<re_restr>古跡</re_restr>
-<re_restr>旧蹟</re_restr>
-</r_ele>
@@ -26,2 +13,0 @@
-<re_restr>旧跡</re_restr>
-<re_restr>旧蹟</re_restr>
@@ -30,5 +15,0 @@
-</r_ele>
-<r_ele>
-<reb>こせき</reb>
-<re_restr>古跡</re_restr>
-<re_restr>古蹟</re_restr>
@@ -38,0 +20,2 @@
+<gloss>historic site</gloss>
+<gloss>place of historical interest</gloss>

I only see ふるあと in koj and nikk. It probably shouldn't be the first reading.

I don't see a source for ふるあと[旧蹟]; I think that reading only applies to 旧跡 and 古跡.

〈旧／古〉〈跡／蹟／迹〉

Google N-gram Corpus Counts
╭─ーー─┬─────────┬───────╮
│ 旧跡 │ 105,953 │ 81.3% │
│ 古跡 │  15,483 │ 11.9% │
│ 旧蹟 │   4,866 │  3.7% │
│ 古蹟 │   4,002 │  3.1% │
│ 古迹 │      60 │  0.0% │ - (jitenon; こせき)
│ 旧迹 │      24 │  0.0% │ - (smk, nikk; きゅうせき)
╰─ーー─┴─────────┴───────╯

It may be best to split the 古 forms into a new separate entry.
The only shared reading is marginal and outdated.

古跡；古蹟；古迹
こせき；ふるあと[古跡]

旧跡；旧蹟；旧迹
きゅうせき；ふるあと[旧跡]